High power LEDs are commonly used in luminaires—for example in the architectural lighting industry in stores, offices and businesses as well as in the entertainment industry in theatres, television studios, concerts, theme parks, night clubs and other venues. These LEDs are also being utilized in automated lighting luminaires with automated and remotely controllable functionality. For color control it is common to use an array of LEDs of different colors. For example a common configuration is to use a mix of Red, Green and Blue LEDs. This configuration allows the user to create the color they desire by additively mixing appropriate levels of the three colors. For example illuminating the Red and Green LEDs while leaving the Blue extinguished will result in an output that appears Yellow. Similarly Red and Blue will result in Magenta, and Blue and Green will result in Cyan. By judicious control of these three controls the user may achieve any color they desire within a color gamut. More than three colors may also be used and it is well known to add an Amber or White LED to the Red, Green and Blue to enhance the color mixing and improve the gamut of colors available.
The differently colored LEDs may be arranged in an array in the luminaire where there is physical separation between each LED, and this separation, coupled with differences in die size and placement for each color, may affect the spread of the individual colors and results in objectionable spill light and/or color fringing of the combined mixed color output beam. It is common to use a zoom lens or other optical device in front of each LED to allow the user to control the beam shape and angle of the output beam; however these optical devices commonly have differing effect for different colors and color fringing or other aberrations may be visible in the output beam. It would be advantageous to have a system where the beam angle is remotely variable and where stray light and aberrations are well controlled.
There is a need for a beam control system for an LED array based luminaire which can be remotely variable and provide improvements in spill light reduction and beam angle control.